The present invention relates to a flow-cell device and, more particularly, to a flow-cell device suitable for use in cellular analysis of living bodies.
Hitherto, apparatus has been known for conducting cellular analysis of living bodies by causing cells extracted from a living body to flow in a flow-cell device while effecting photometry of the cells. In this apparatus, generally known as a flow-cytometer, a light beam is applied to cells in the suspension of cells and, on the basis of scattering light and fluorescence from the cells, the analyses of the sizes, shapes and other state of cells are conducted.
In operation of the flow-cytometer, in order to pour the suspension of cells through a capillary flow passage for measurement with stability and without clogging, a method has been adopted in which the suspension of cells is made to flow by being surrounded by physiological saline physiological SaH solution. The method will be described with reference to FIG. 10. FIG. 10 shows a concept of the method. In FIG. 10, the suspension of cells 1, namely, sample fluid is surrounded by the physiological saline 2, namely, sheath fluid. That is, sheath fluid flow is formed around sample fluid flow and the sample fluid flow becomes a laminar flow. The sample fluid and the sheath fluid are discharged from a discharge port 3 to the exterior.
This method is referred to as "sheath-flow method", and constitutes an effective measure in the cellular analysis, but involves the following disadvantages. Forces 4 as shown in FIG. 10 act on the cells in the suspension from the surfaces of the capillary flow passage surfaces and physiological saline, so that flat cells such as red carpuscles are oriented at random in the measuring portion, with the result that the measurement data of scattered light and fluorescence fluctuate undesirably.
Two measures have been taken for the purpose of overcoming these problems. One of these measures is to introduce a variation in the length-to-breadth ratio between the flow-contracting portion and the capillary flow passage as shown in FIG. 11, so as to vary the magnitudes of the forces acting on the flowing cells in the longitudinal and breadthwise directions, thereby to uniformly orient the flat cells. This method is discussed in the Journal of Histochemistry and Cytochemistry, Vol. 25, No. 7 (1977) pp. 774-780.
Another measure is to adopt a wedge-shaped form on the end of a nozzle 5 through which the suspension of cells (sample fluid) is discharged into the flow of the sheath fluid, as shown in FIGS. 12A and 12B. FIG. 12A is a perspective view of the nozzle 5. FIG. 12B is a sectional view of the flow-cell showing the state of flow of the sample fluid 1 and the sheath fluid 2 supplied from the nozzle 5. As shown in FIGS. 12A and 12B, by using a wedge-shaped form on the end of the nozzle 5, the sample fluid flow in the sheath fluid flow becomes flat. Therefore, it is possible to confine the flat cells in the flat flow of the sample fluid. This method is described in detail in "Biophysics Journal", Vol. 23 (1978) pp. 7-13.
The prior art techniques described involve the following problems. Namely, in the method of FIG. 11 relying upon variation of the length-to-breadth ratio of the cross-section of the flow-cell, the ratio between the forces acting on the cell in the longitudinal and breadthwise directions is constant, so that the cell receives rotational moment depending on the initial posture of the cell discharged from the nozzle. In consequence, the cells fail to be oriented in the same direction.
On the other hand, the known art relying upon wedge-shaped form of the suspension explained with reference to FIGS. 12A and 12B has a drawback in that the flattened flow of the suspension tends to be twisted in the form of a ribbon, even by a slight turbulence of the sheath fluid (physiological saline), with the result that the measurement of the flat cells in the constant direction is failed.
Obviously, the fact that the flat cells cannot be measured stably in flat positions impairs the precision of the data obtained through the measurement conducted at the photometry section.